Is postmodern art a passing phase of nonsense or an exciting and innovative treasure?

The reasons you can argue that postmodernist art is a passing phase of nonsense are that it breaks from traditions in the history of art, seeking to produce something that cannot be understood through the lens we use to look at traditional art. If we are looking at postmodern art through the lens we use to understand Renaissance art, it seems like nonsense. This is because the goals of Renaissance art and the goals of postmodernist art are not the same. Renaissance art wants to show the most accurate depiction of the human form, of nature, and anything else we see in the world, even if it is attempting to paint something supernatural (see for example how Michelangelo depicts heaven in his ceiling for the Sistine Chapel). We could say that Renaissance art wants to give answers (to questions such as what heaven looks like, for example), but postmodernist art wants to ask questions. For that reason, we could argue that it is not a passing phase of nonsense but an exciting and innovative treasure. Postmodernist art offers a new perspective of the world and tries to give shape to abstract concepts and ideas. Andy Warhol's soup cans, for example, ask us to consider if soup cans could be art. Art becomes an abstract idea in that case, because if we are asking this question, then it suggests we do not already know what art is. Duchamp's readymades ask the same questions--is this art or not? Can a urinal be art? Instead of looking out at the world and showing what the world looks like, as Renaissance art does, postmodernist art looks in on itself, asking what art is.

We could also argue that it is an exciting and innovative treasure because after the industrial revolution and the rise of the city and of the science of psychology (all of which happened within 100 years), people's roles in life shifted. It became more common for people to want to seek out their identities outside of their jobs and families, asking "Who am I? What is the essence of my identity?" Postmodern art is reflecting this moment in history, asking the same questions of itself. 

If we consider postmodern art from the perspective we use to consider Renaissance art, it will seem like nonsense. If we consider it from a historical perspective or a perspective of questioning what art is, it seems like an exciting and innovative treasure.